Capacitat d'adsorció sobre sílice de complexos de tipus [Ru(bpy-R)3]2+ en funció de la natura dels lligands

Abstract

n this bachelor thesis, various ruthenium compounds with bidentate bipyridine-type ligands, of

the formula 4,4'-R-2,2'-bipyridine (with R = CH3 or COOH), were synthesized. First, the

compounds [RuCl2(bpy)2] and [RuCl2(dmso)4] were synthesized as precursors for compounds

[Ru(bpy)2(bpy-CH3)](PF6)2,[3], [Ru(bpy-CH3)3](PF6)2, [4] i [Ru(bpy)2(bpy-COOH)](PF6)2, [5], which

were obtained with good yields. Subsequently, the complexes [3], [4], and [5] were

characterized using 1

H-NMR, ESI-MS, UV-Vis, and cyclic voltammetry techniques.

The 1

H-NMR spectra recorded in acetone-d6 show that compounds [3] and [5] have a C2

symmetry axis, while compound [4] has three C2 axes passing through the center of the bpy-R

ligands and the ruthenium atom. Additionally, the presence of electron-withdrawing groups in

the bpy-COOH ligand causes the signals of the ligand itself to appear particularly deshielded.

ESI-MS analysis was also performed for compounds [3], [4], and [5], detecting ions

corresponding to the cationic part of the compounds for all three, in some cases forming

adducts. For compounds [3] and [4], a +1 charge peak was also observed, indicating the presence

of an adduct where the compounds have lost only one of the PF6

– counterions. On the other

hand, for compound [5], only the peak corresponding to the dication is observed, along with

other +2 charge ions, which can be assigned to different adducts of the compound with Na+ and

K+ cations, originating from the deprotonation of the bpy-COOH ligand's acidic groups.

The electrochemical properties of compounds [1], [3], [4], and [5] were also studied using cyclic

voltammetry. The four compounds have electrochemically reversible waves corresponding to

the Ru(III/II) redox pair.

The UV-Vis spectrum of compounds [3], [4], and [5] in acetone was recorded. Bands were

observed at λ values around 450-460 nm, corresponding to metal-to-ligand charge transfer

(MLCT) transitions. Finally, UV-Vis spectroscopy was also used to monitor the adsorption of the

three compounds on a silica-type support. It was determined that the number and nature of the

substituted bpy-R ligands determine the ability of each complex to incorporate into the silica

matrix